Effect of molecular shape of diisocyanate units on the microscopic/macroscopic phase separation structure of polyurethanes

Abstract

Three diisocyanate units having different linearity and planarity on the basis of the arrangement of constituent aromatic rings are used to synthesize three polyurethanes (PUs) and the effects of the molecular structure of the diisocyanate units on phase separated morphologies of PUs have been studied. The linear and planar diisocyanate unit allows good packing of the hard segments in the hard domain by extensive intersegmental hydrogen bonding, and it forms a well ordered, long hard domain. However, the nonlinear and noncoplanar diisocyanate unit shows a lesser degree of hydrogen bonding in the short hard domain. Strong preferential orientation of the rigid/long hard domains inside a macroscopic grain boundary has been observed with the polarizing optical microscope especially for the PU based on the rigid diisocyanate. It was concluded that the molecular structure of the diisocyanate unit in PU plays an important role in determining the interchain interaction, the detailed phase‐separated domain structure, and local domain orientation in each grain boundary. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011

A Polyurethane Surface Modifier: Contrasting Amphiphilic and Contraphilic Surfaces Driven by Block and Random Soft Blocks Having Trifluoroethoxymethyl and PEG Side Chains

“…Somewhat increased phase separation is suggested by the −40 °C T g for 3F‐U. Several factors contribute to improved phase separation in polyurethanes including the shape and symmetry of the hard block, which influences the extent of hydrogen bonding 68, 69. Considering the 3F soft block T g 's for the MDI/BD and IPDI/BD polyurethanes and the different symmetries of the hard block, immiscibility appears to be driven by a synergistic combination of MDI hard block crystallization ( T m ≈ 186 °C) and the lack of phase mixing of the fluorous soft block.…”

Dielectric properties of segmented polyurethanes for electromechanical applications

“…They are synthesized by the same industrial process from the same initial The SS originate from the polyol and are responsible for the elastomeric behaviour of the polymeric material; the HS contain highly polar urethane linkages and it is thought[14,15,16,17] that due to phase separation they form highly polar and stiff microdomains embeddedin a soft poorly polar matrix. Essentially, the morphology of the segmented polyurethanes depends on the relative amount of the soft and hard segments and on other physical phenomena such as crystallization and hydrogen bonds formation between the two types of segments.…”

Microphase separation and mechanical properties of the polyurethanes based on the high soft segment poly(bis‐azidomethyl oxetane)/tetrahydrofuran binder

“…According to the FTIR spectra, the hydrogen bonding fraction of the prepared p(BAMO/THF) polyurethanes in C=O units ( f H.B ) can be quantitatively calculated by Eq . : …”

“…The lower modulus and higher flexibility are due to the much amorphous domains in synthesized samples, which have also been reported in present work . A plastic deformation and strain‐induced crystallization phenomena were not observed in the HBP, which is different from other results , this is due to the lower crystalline structure did not have a hindrance effect over the whole homogeneous polyurethane network of HBP. The relatively higher ductility results in the lower tensile strength of HBP, compared to other polyurethanes.…”